1. Field of the Invention
The present invention relates generally to a mechanism for steering an articulated vehicle and more particularly to a mechanism for steering a vehicle with a plurality of pivotally connected sections without steering the vehicle wheels.
Many articulated vehicles such as earthmovers and tractors, carry large loads which require the transmittal of large amounts of power to all of the vehicle wheels. The vehicles may be equipped with shovels or other tools, such that steering the vehicle wheels is impractical. These vehicles may be steered by exerting forces between adjacent sections of the vehicle to swing one section relative to another section about an articulation joint.
This may be accomplished by piston and cylinder steering arrangements which are usually hydraulic and which act on each side of the vehicle to swing the vehicle sections relative to each other. Piston and cylinder steering arrangements are usually connected between vehicle sections so that the extension of the device on one side of the vehicle causes the vehicle to bend toward the opposite side. Likewise, compression of the piston and cylinder steering arrangement on one side of the vehicle causes the vehicle to bend toward the same side. Extension and compression of the piston and cylinder arrangements on opposite sides of a vehicle can be coordinated to turn the vehicle.
A steering mechanism as described above has a number of disadvantages. The piston and cylinder arrangements are located on the exterior of the vehicle and are therefore exposed to damage by contact with other equipment and with stationary objects. The angle between each piston and cylinder arrangement and its mountings on the vehicle constantly change as the vehicle is steered which alters the steering torque. Additionally, if it is decided to use an articulation joint having a large diameter, for reasons of rigidity or otherwise, it may be impossible to mount piston and cylinder steering arrangements on a vehicle without substantially increasing the dimensions of the vehicle, which is often disadvantageous.